As part of the ongoing development of commercial aircraft and other vehicles that are becoming increasingly more complex, there is an endeavor to continuously improve both operability and reliability. In order to ensure this, for example, for commercial aircraft to be used in the future, improvements in maintainability and the reduction in maintenance costs are generally relevant. In this context an important step could relate to the possibility of carrying out even unscheduled maintenance work quickly and in an uncomplicated manner.
As an energy transmission system or power transmission system for operating actuators, landing gear, brakes and doors or flaps of a commercial aircraft, a hydraulic system depends on the quality and the state of a hydraulic fluid used, because said hydraulic fluid establishes the mechanical connection between the energy source in the form of hydraulic pumps or other means and the consumers. In the assumption that the service life of a hydraulic fluid may extend to a large part of the intended aircraft service life or could even exceed the aforesaid, provisions must be made that can ensure the quality of the hydraulic fluid.
In the case of hydraulics fluids based on phosphate ester, which are at present commercially available, the water content comprises a significant factor influencing the state of the hydraulic fluid. Under the influence of increased temperatures the water content accelerates ageing of the hydraulic fluid as a result of an increased acid content. When the hydraulic fluid reaches the end of its service life, required physical characteristics may no longer meet system requirements. If this is the case, replacement of the hydraulic fluid is the logical consequence. Influencing the hydraulic fluid as a result of impurities such as particles or suspended solids can be eliminated by filtering so that in this case it does not become necessary to change the entire fluid.
In order to always be able to make a reliable statement relating to the quality and the state of ageing of hydraulic fluids, samples are regularly taken from a respective hydraulic system, for example in aircraft at each second C-check. More detailed information can usually be found in a maintenance manual for the particular aircraft type.
DE 196 19 028 C2 and U.S. Pat. No. 5,858,070 A show a device for cleaning a hydraulic fluid by means of a flinger disc arrangement so that the provision of an exchange quantity of hydraulic fluid may be omitted. Other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.